Krypton Gas
A dense inert gas used in high-performance IGUs, providing better thermal insulation than argon but at significantly higher cost.
Krypton is approximately 64% less conductive than air (compared to argon at 34%), making it the premium gas fill option for IGUs. It is most commonly used in triple-pane units where the narrower cavity (typically 8-10 mm) makes argon less effective — krypton performs optimally in narrower gaps than argon.
Due to its high cost (roughly 10 times the price of argon), krypton fill is typically reserved for high-performance applications such as passive house windows and northern climate installations where achieving very low U-values is critical.